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How to calculate the mean of an image?

Asked by bh dhouha on 16 Feb 2015
Latest activity Commented on by Kweku Nkrumah on 15 Jun 2018
How to calculate the mean of an image? Does the code mean2(img) give the right result?

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2 Answers

Answer by Image Analyst
on 16 Feb 2015
 Accepted Answer

To calculate the mean of all pixels in the image, without regard to what color channel they came from (if it's a color image), you do
meanIntensity = mean(img(:));
What you did will not do it, as I'm sure you found out.

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Thank you very much :) just a little thing : i used mean(mean(img1(:,:,1)))and it gave me the same result as mean(img1(:)).The first code is focused on the red channel only i think-as you answered me in another question- so how could it be the same result?
It could be the same if the image was gray since the blue and green channel would be identical to the red channel. It would also be the same for lots of other cases, like where the green and blue channels are scrambled (spatially rearranged) versions of the red channel since they would have the same pixel values regardless of how they're rearranged.

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Answer by Rashmi.D Jeya kumar on 8 Jan 2018

meanval = mean2(I) you can get mean value of an image

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Hello. I used the above code (meanval=mean2(I)) for finding the mean of different images. Over sometime, it gave me the same value for the mean of most of the images. What could be wrong?
Why does that mean anything is wrong? Maybe you took a bunch of photos through a microscope and they all have the same mean brightness (or really close to each other). Doesn't seem inherently unusual to me. Why do you think it indicates something is wrong?
Ok. I get it now. Thank you.

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